This invention relates to filter cartridges for drinking water treatment systems, and more specifically to a filter cartridge for use with a precoat style filter media, and having a device for providing or introducing a soluble compound into the filtered water.
This invention deals with a water treatment cartridge of the type disclosed in U.S. Pat. Nos. 4,857,189 and RE 34,031, both of which are incorporated by reference herein. These cartridges disclose a precoat style of filtration where the treated, activated carbon media filters the water, and in so doing adheres to a bag-like, porous filter septum located in the cartridge. As water enters an inlet to the cartridge and proceeds through an inlet passage, it moves through the filter media, then through the septum and out through an outlet stack and an outlet.
It is common to add a phosphate compound to filtered water to reduce scaling caused by hard water. In conventional applications, phosphate addition is accomplished concurrently with filtration by dissolving a solid phosphate compound in a small portion of the water flowing through the water treatment cartridge. The phosphate crystals are held in a feeder tube, and a small portion of the filtered water is fed through the feeder tube, dissolving some of the phosphate crystals. The phosphate-containing water then exits through a bleed hole to the outlet stack, where it is combined with the remainder of the filtered water.
In the prior art, phosphate addition is accomplished by use of a feeder tube that is fed by a portion of the water that has already been filtered. A xe2x80x9cflowerpot assemblyxe2x80x9d is located near the top of the filter cartridge with an opening facing upward so that gravity or turbulence does not pull out filter media in the orifice from the inlet tube. This flowerpot assembly also houses filtering material between the opening and the check valve. A portion of the filtered water flows through a valve in the flowerpot assembly to the feeder tube by means of ABS tubing. The tubing is secured at both ends with a solvent such as methyl ethyl ketone (MEK) to hold the tubing to the outlet of the flowerpot assembly and the inlet of the feeder tube. The tubing is press fit onto a connector on either end and is then secured with a chemical solvent to ensure the connection. A grid screen and compression ring are used to prevent phosphate crystals from plugging the flow path in the bent tube, requiring another solvent bond.
The preferred solvent is MEK. This solvent ensures a physical as well as a sealed connection. Establishing a sealed connection is important because the water must go through the ABS tubing to the feed tube, and must not bypass the flowerpot.
However, the use of a solvent such as MEK creates numerous problems in the manufacture and use of the water treatment cartridges. First of all, the solvent is time consuming to apply manually. Also, during manufacture, time is needed for the adhesive to dry, further elongating the process. Finally, there is a possibility that an MEK-fluidized ABS bubble may form, blocking the flow path in the plastic tube. Parts are fixtured to blow air through to break bubbles that may form. This procedure takes time and materials. Thus, there is a need for a fewer connections which are easier and less time consuming to assemble during manufacture.
Use of the flowerpot assembly and ABS tubing to feed water to the feeder tube requires the use of several components that may be unnecessary. These components, including the flowerpot housing, tubing, grid screen and compression ring must be purchased, warehoused, stocked and available during the manufacturing process. Elimination of these parts would result in a filter cartridge that is less expensive and easier to manufacture.
There is also a disadvantage to the prior art construction once the cartridge is in use. By using the MEK solvent, there is a concern by some that it might enter into the treated water. Since the purpose of water filtration of this type is to clean the water, the possibility of the solvent contaminating the water is a problem. The delivery of water into the feeder tube must be done without the introduction of solvents into the water.
Accordingly, an object of this invention is to provide a new and improved feeder tube for a water filter cartridge that draws untreated water for treatment by a solid compound.
Another object of this invention is to provide an improved feeder tube construction that establishes fluid communication with the filter cartridge that is easier and less time consuming to assemble during manufacture.
Yet another object is to provide an improved filter cartridge requiring no use of chemical solvents.
It is still another object of this invention to provide an improved water filter cartridge that has fewer parts and is less expensive to manufacture.
These and other objects are met or exceeded by the present invention which features a feeder tube which draws a desired portion of unfiltered water through a plug assembly for treatment by a solid compound. The plug assembly filters and purifies the water before it is exposed to treatment by the solid compound.
More specifically, the present invention features an improved feeder tube for a water treatment cartridge that provides treatment by a solid compound for a slipstream of untreated water flowing through the cartridge. The feeder tube includes a first end and a second end, such that the slipstream of water generally flows into the feeder tube at the second end and out of the feeder tube at the first end. A bottom plug assembly is in operational relationship with the second end and includes a porous plug being sized and configured to provide filtration and purification for the slipstream portion of the water.
When in operation, the slipstream of untreated water is filtered and purified by the porous plug. It then passes through the valve into the feeder tube where it reacts with the solid compound. The filtered and treated water then exits the feeder tube through the bleed hole. Drawing of untreated water directly into the feeder tube eliminates the need for the tubing, grid screen, compression ring and flowerpot housing of the prior art. Since the filtration system of the water filter cartridge is simpler, it is faster and less costly to manufacture.
Further, the tubing of the prior art was attached to the flowerpot assembly and the feeder tube by solvent bonds. The present invention is faster and easier to produce because there are no connections of this type. When there are no solvent bond connections, there is also no opportunity for MEK-fluidized ABS solvent bubbles to block water flow and no application of special procedures to prevent blockage of water flow. Each of these factors makes the present feeder tube less expensive to produce.
Eliminating the use of MEK solvent also results in cleaner product water. When no solvent is used in making the filter cartridge, there is no opportunity for MEK to leach into the water. Less contamination produces cleaner water as it exits the filter cartridge.